1. Technical Field
The present disclosure relates to a muscular fatigue determination apparatus, a method for determining muscular fatigue, and a recording medium that generate muscular fatigue information regarding a user and that determine presence or absence of muscular fatigue or a level of muscular fatigue on the basis of a relationship between a load applied to a pedal, the rotation speed of a crank, and the myoelectric potential of the user while the user is rotating the crank by stepping on the pedal of a bicycle or a cycle trainer.
2. Description of the Related Art
There have been a lot of studies on myoelectric potential. Due to characteristics of myoelectric potential, the amplitude of myoelectric potential increases as muscular output increases, and the amplitude of myoelectric potential decreases as muscular output decreases. If muscular fatigue occurs, more exercise units (muscle fibers) than before the occurrence of the muscular fatigue are needed to generate the same force (in the case of an isometric exercise), and the amplitude of myoelectric potential increases. In the case of an isometric exercise, an average frequency of myoelectric potential decreases as muscle fatigues.
Some methods for evaluating a state of muscle during exercise or the like on the basis of the characteristics of myoelectric potential have been proposed. In Japanese Unexamined Patent Application Publication No. 2000-000232, for example, a method for determining muscular fatigue during driving has been proposed. An electrical stimulation electrode pulse voltage is applied to a muscle of a driver, an evoked myoelectric potential caused by the application of the pulse voltage is measured, a power spectrum of the evoked myoelectric potential is obtained, and a center frequency of the power spectrum is calculated and stored as an initial value. The same operation is performed at certain time intervals, and it is determined whether muscular fatigue has occurred on the basis of changes in the center frequency of the power spectrum.
In Japanese Unexamined Patent Application Publication No. 2007-312921, a method for determining whether a user has appropriately recovered from exercise has been proposed. Before beginning the exercise, the user performs an isometric exercise to measure a myoelectric potential. After the exercise, the user performs an isometric exercise to measure a myoelectric potential again with the same load as in the isometric exercise performed before the exercise. It is then determined whether the user has appropriately recovered from the exercise by comparing the second myoelectric potential with the first myoelectric potential.